1. Field of the Invention
The present invention relates to a folding box for packing, which is made from a high density foam polypropylene resin board and used mainly as a folding box for packing for transporting things in the physical distribution industry and secondarily as a storage box for arranging things in order for the purpose of tidying up a room.
2. Description of the Related Art
In a recent industry field of living, there have been strong demands for natural environmental protection and for reasonable and economical utilization of limited resources. It is known that, in response to the above-described demand, there is a growing tendency to make an effort so that persons living lives, manufacturers of goods and users of goods would respectively cooperate each other.
Especially in the physical distribution industry, a conventionally used folding box for packing made of cardboard has a problem in weather resistance, durability and sanitary usage although a cost of used materials is cheep. Therefore, the folding structure of the above folding box is designed only for securing economy of space for storing and returnability in several times. The folding boxes are collected at a certain cost to make recycled paper or are incinerated, after being used several times until they cannot be used any more.
From the above point of view, the present inventor has developed a folding box for packing made from a high density foam polypropylene resin board in view of durability as well as light weight and low cost of the box and has already filed a patent application (No. 338632/2000) for the above folding box for packing and its manufacturing method and apparatus.
As described above, a folding box for packing made from a high density foam polypropylene resin board can satisfy demands for weather resistance, sanitary usage, light weight and durability as well as enable not only recycle but also long-term returnability and reuse to be achieved. It has been newly revealed, however, that the elastic characteristic of the above high density foam polypropylene resin board does not sufficiently contribute to reduction in volume of the folded boxes in storage and transportation (collection) and to improvement in efficiency of folding and assembling (into a three-dimension) operations.
This is caused by the elastic characteristic of the above-described material to be used and by difficulty of a high density foam polypropylene resin board in pretreatment of adhering (such as cleaning and surface-roughing treatments) and control of application of adhesive such that a connecting member such as a staple and an eyelet should be used for connecting overlapping surfaces of edges to be connected. Elastic memory operates on a bending part of the folded box, so that respective box forming bodies continuous at the bending parts would rise up toward a rising direction rather than overlap closely each other. The volume of the folded box thus becomes large, compared with a completely flatted condition (a condition of overlapping closely to be flatted). On the other hand, strength in supporting is required for assembling bottom forming boards. Therefore, in folding and assembling operations, the efficiency is deteriorated in assembling and flatting cover-forming boards and bottom forming boards, especially in assembling and flatting bottom forming boards.
In addition to the above, there is a danger that a careless operation would cause an operator to be damaged due to popping up of box forming bodies, for example. Moreover, the material to be used may be weakened by repeating assembly and disassembly for flatting of the bottom forming boards. These would cause difficulty in achieving returnability and reuse notwithstanding the usage of a high density foam polypropylene resin board.
There was a simple judgment that the above-described disadvantages caused by using a high density foam polypropylene resin board to form a folding box for packing can be solved by employing an auto bottom structure, which is popularly employed for a folding box for packing made of cardboard, (the structure in which bottom forming boards of a box are connected in advance in a flat shape so as to naturally form a horizontal bottom as they are when the box is assembled into a three-dimension) for a folding box for packing made from a high density foam polypropylene resin board. Simply employing the auto bottom structure, however, cannot solve the most of the above-described disadvantages.
That is, due to the auto bottom structure similar to that of a folding box for packing made of cardboard, elastic memory largely operates on a bending part of a folded box, so that respective box forming bodies, which are continuous at the bending parts, would rise up toward a rising direction, and thereby, the volume of the box becomes large even after flatting the box and the strength of the box decreases. This large volume and decreased strength may cause deterioration of the folding box for packing in economy of physical distribution, in packing functionality and in efficiency of a handling operation. Furthermore, as described above, there is a difficulty in adhering a high density foam polypropylene resin board by means of adhesion, so that the box cannot maintain the required strength unless a connecting member such as a staple and an eyelet is used. Thus, the elastic characteristic of a high density foam polypropylene resin board blocks solution of the above problems.
In a connecting operation by means of a staple or an eyelet, the boards should be connected by sandwich from both of the inside and the outside of a folding box since one of outside surfaces in respect with the overlapping surfaces forms an inner surface of the folding box. This makes the connecting operation very troublesome, and in addition, there are problems that the staples or eyelets are exposed inside and outside the box, so that the security in operation and the appearance of the box would be damaged and so that dust would be allowed to enter the box to contaminate the contents. Especially, there is a most important problem in recycling components of the box since components to be recycled are required to be of a single material while the above staples or eyelets are made of a different material from that of the components of the box.
The danger in the operation, the damage in appearance of the box and the most important problem in recycle can be solved by employing a high frequency welding method between overlapping surfaces of edges to be connected. This method, however, requires electrodes to be opposed each other on the inside and outside surfaces of the connecting part. Therefore, it is difficult to employ this method since the connecting operation would be troublesome and high frequency welding marks would be visually and clearly recognized on the outer surface of the box, which damages the appearance of the box, similarly to the case of connecting by means of staples and eyelets.
A purpose of the invention is to provide a folding box for packing, which is made from a high density foam polypropylene resin board, having an auto bottom structure as a bottom structure of the folding box for packing, the auto bottom structure being able to satisfy the weather resistance, sanitary usage, light weight and durability inherent in the high density foam polypropylene resin, to secure not only recycle but also long-term returnability and reuse, and to improve economy in physical distribution and efficiency of folding and assembling (into a three-dimension) operations in handling by reducing the volume of the folded box in storage and transportation (collection), without blocked by elastic memory or adhesiveness of the high density foam polypropylene resin.
The invention is to solve the above problems of the related art. Another purpose of the invention is to provide a folding box for packing made from a high density foam polypropylene resin board, in which strength is secured in a connecting part so as to improve the durability, and thereby, long-term returnability is achieved as well as reusability, the efficiency of the connecting operation in relative connecting parts and security in an operation are assured, deterioration in appearance is dissolved, and a single material is used to satisfy a requirement for recycle.
The folding box for packing in accordance with the invention includes two kinds of folding boxes for packing: a folding box for packing in accordance with a first invention, which is made of high density foam polypropylene resin and in which a developed flat box forming board includes four side walls forming a square trunk of the folding box and comprises two box forming bodies (P1) and (P2) respectively comprising a main face wall extendedly provided on one lateral side thereof with a connecting piece for forming the trunk, a side face wall connected with the other lateral side of the main face wall, bottom forming boards extendedly provided to respective lower edges of the above main face wall and the above sub face wall, and cover forming boards extendedly provided to respective upper edges of the above main face wall and the above sub face wall; and a folding box for packing in accordance with a second invention, which comprises one box forming body (P3).
The folding box according to the first invention includes a first box forming body (P1) and a second box forming body (P2), each of the box forming bodies (P1) (P2) respectively including: a main face wall (2) having a connecting piece (1) extending from a first lateral side of the main face wall (2); a sub face wall (3) extending from a second lateral side of the main face wall (2); a first bottom forming board (4a) (4c) extending from a lower edge of the main face wall (2); a second bottom forming board (4b) (4d) extending from a lower edge of the sub face wall (3); a first cover forming board (5b) (5d) extending from an upper edge of the sub face wall (3); the second bottom forming boards (4b) (4d) having a first folding connection piece (9a) and a second folding connection piece (9b), which connect the first bottom forming boards (4a) (4c) with the second bottom forming boards (4b) (4d) (refer to FIGS. 1 and 2).
A side edge of the bottom forming board (4b) (4d) of each sub face wall (3) of the above box forming bodies (P1) and (P2), is made to be an inclined edge (6) having a 45 degrees angle in respect with a border line between the above sub face wall (3) and the second bottom forming board (4b) (4d), and the above inclined edge (6) is extendedly provided with a first folding connecting piece (9a) and a second folding connecting piece (9b) having a line for bending into the shape of a V (8) for erasing an effect of elastic memory of the high density foam polypropylene resin occurring in folding, while respective border lines among the main face walls (2), the sub face walls (3), the cover forming boards (5a) (5b) (5c) (5d), the bottom forming boards (4a) (4b) (4c) (4d), and the connecting piece (1) of the above box forming bodies (P1) and (P2) are made to be lines for bending into the shape of a mountain for erasing an effect of elastic memory of the high density foam polypropylene resin occurring in folding and assembling the folding box.
And the above set of two box forming bodies (P1) and (P2) are mutually connected (refer to FIG. 9) by heat and pressure-fusion between a back surface of the sub face wall (3) of the first box forming body (P1) and a front surface of the connecting piece (1) of the second box forming body (P2) opposing the above back surface, between a back surface of the sub face wall (3) of the second box forming body (P2) and a front surface of the connecting piece (1) of the first box forming body (P1), between a back surface of the first folding connecting piece (9a) extendedly provided to the second bottom forming board (4b) and a front surface of the first bottom forming board (4a) of the main face wall (2) of the first box forming body (P1), opposing to the back surface of the first folding connecting piece (9a), and between a back surface of the second folding connecting piece (9b) extendedly provided to the second bottom forming board (4d) and a front surface of the first bottom forming board (4c) of the main face wall (2) of the second box forming body (P2), opposing to the back surface of the second folding connecting piece (9b), the back and front surfaces overlapping in a bottom forming structure in assembling the folding box.
The first invention is characterized in that lines for bending into the shape of a mountain (7c) are provided between the main face wall (2) and the first cover forming board (5a) of the first box forming body (P1), between the sub face wall (3) and the second cover forming board (5b) of the first box forming body (P1), between the main face wall (2) and the first cover forming board (5c) of the second box forming body (P2) and between the sub face wall (3) and the second cover forming board (5d) of the second box forming body (P2), including side grooves (74) on both sides of a middle groove (72) through partitions (73), and said side grooves (74) and said middle groove (72) are disposed on an exterior surface of the folding box; lines for bending into the shape of a mountain (7a) are provided between the main face wall (2) and the sub face wall (3) of each box forming body (P1) (P2), including two side grooves (74) parallel to a border line and a wide ridge (71a) between the two side grooves (74), a width of the wide ridge (71a) being about twice a thickness of the main face wall (2), and said side grooves (74) and said wide ridge (71a) are disposed on an exterior surface of the folding box; and lines for bending into the shape of a mountain (7b) are provided between the connecting pieces (1) and the main face walls (2), between the main face walls (2) and the first bottom forming boards (4a) (4c), and between the sub face walls (3) and the second bottom forming boards (4b) (4d), including two side grooves (74) parallel to a border line and a narrow ridge (71b) between the two side grooves (74), and said side grooves (74) and said narrow ridge (71b) are disposed on an exterior surface of the folding box.
The folding box for packing in accordance with the second invention is made of high density foam polypropylene resin, as clearly seen in FIG. 17, and in this folding box, a developed flat box forming board includes four side walls forming a square trunk of the folding box and comprises one developed box forming body.
The above one box forming body (P3) includes a first main face wall (21); a connecting piece (1) extending from a first lateral side of the main face wall (21); a first cover forming board (5a) extending from an upper edge of the first main face wall (21); a first bottom forming board (4a) extending from a lower edge of the first main face wall (21); a first sub face wall (31) extending from a second lateral side of the first main face wall (21); a second cover forming board (5b) extending from an upper edge of the first sub face wall (31); a second bottom forming board (4b) extending from a lower edge of the first sub face wall (31); a second main face wall (22) extending from a lateral side of the first sub face wall (31); a third cover forming board (5c) extending from an upper edge of the second main face wall (22); a third bottom forming board (4c) extending from a lower edge of the second main face wall (22); a second sub face wall (32) extending from a lateral side of the second main face wall (22); a fourth cover forming board (5d) extending from an upper edge of the second sub face wall (32); and a fourth bottom forming board (4d) extending from a lower edge of the second sub face wall (32), the second bottom forming board (4b) having a side edge made to be a first inclined edge (6a) having a 45 degree angle in respect with a border line between the first sub face wall (31) and the second bottom forming board (4b), the fourth bottom forming board (4d) having a side edge made to be a second inclined edge (6b) having a 45 degree angle in respect with a border line between the second sub face wall (32) and the fourth bottom forming board (4d), the first inclined edge (6a) being extendedly provided with a first folding connecting piece (9a), the second inclined edge (6b) being extendedly provided with a second folding connecting piece (9b).
The respective border lines among the respective main face walls (21) and (22), the respective sub face walls (31) and (32), the cover forming boards (5a) (5b) (5c) (5d), the bottom forming boards (4a) (4b) (4c) (4d), and the connecting piece (1) of the above box forming body (P3) are made to be lines for bending into the shape of a mountain for erasing an effect of elastic memory of the high density foam polypropylene resin occurring in folding and assembling the folding box.
A front surface of the above connecting piece (1) and a back surface of the second sub face wall (32) opposing to the above front surface are melted by heating, and back surfaces of the folding connecting pieces (9a) (9b) extendedly provided to the bottom forming boards (4b) (4d) of the above respective sub face walls (31) and (32) and front surfaces of the bottom forming boards (4a) (4c) of the main face walls (21) (22) opposing to the back surfaces of the folding connecting pieces (9a) (9b), the back and front surfaces overlapping in a bottom forming structure in assembling the folding box, are melted by heating, and then, the melted surfaces are superposed each other to be pressured, so that the back and front surfaces would be connected in such a fusion method.
[Effect of the First Invention]
According to the first invention, in a folding box for packing made of high density foam polypropylene resin with auto bottom structure including a first box forming body (P1) and a second box forming body (P2), each of the box forming bodies (P1) (P2) respectively including: a main face wall (2) having a connecting piece (1) extending from a first lateral side of the main face wall (2); a sub face wall (3) extending from a second lateral side of the main face wall (2); a first bottom forming board (4a) (4c) extending from a lower edge of the main face wall(2); a second bottom forming board (4b) (4d) extending from a lower edge of the sub face wall (3); a first cover forming board (5a) (5c) extending from an upper edge of the main face wall (2); and a second cover forming board (5b) (5d) extending from an upper edge of the sub face wall (3), wherein the second bottom forming board (4b) (4d) extending from the sub face wall (3) has a side edge adjacent to the first bottom forming board (4a) (4c) extending from the main face wall (2), the side edge being an inclined edge (6) having a 45 degree angle in respect with a border line between the sub face wall (3) and the second bottom forming board (4b) (4d), with the inclined edge (6) including a first folding connecting piece (9a) and a second folding connecting piece (9b) having a linear region bendable into the shape of a V (8) for reducing an effect of elasticity of the high density foam polypropylene resin occurring in folding, wherein the two box forming bodies (P1) (P2) are mutually connected by heat and pressure-fusion between a back surface of the sub face wall (3) of the first box forming body (P1) and a front surface of the connecting piece (1) of the second box forming body (P2), between a back surface of the sub face wall (3) of the second box forming body (P2) and a front surface of the connecting piece (1) of the first box forming body (P1), between a front surface of the first bottom forming board (4a) and a back surface of the first folding connecting piece (9a) of the first box forming body (P1) and between a front surface of the first bottom forming board (4c) and a back surface of the second folding connecting piece (9b) of the second box forming body (P2); the improvement comprising: lines for bending into the shape of a mountain (7c), between the main face wall (2) and the first cover forming board (5a) of the first box forming body (P1), between the sub face wall (3) and the second cover forming board (5b) of the first box forming body (P1), between the main face wall (2) and the first cover forming board (5c) of the second box forming body (P2) and between the sub face wall (3) and the second cover forming board (5d) of the second box forming body (P2), including side grooves (74) on both sides of a middle groove (72) through partitions (73), and said side grooves (74) and said middle groove (72) are disposed on an exterior surface of the folding box; lines for bending into the shape of a mountain (7a), between the main face wall (2) and the sub face wall (3) of each box forming body (P1) (P2), including two side grooves (74) parallel to a border line and a wide ridge (71a) between the two side grooves (74), a width of the wide ridge (71a) being about twice a thickness of the main face wall (2), and said side grooves (74) and said wide ridge (71a) are disposed on an exterior surface of the folding box; and lines for bending into the shape of a mountain (7b), between the connecting pieces (1) and the main face walls (2), between the main face walls (2) and the first bottom forming boards (4a) (4c), and between the sub face walls (3) and the second bottom forming boards (4b) (4d), including two side grooves (74) parallel to a border line and a narrow ridge (71b) between the two side grooves (74), and said side grooves (74) and said narrow ridge (71b) are disposed on an exterior surface of the folding box. Thus, the two box forming bodies (P1) and (P2) can be connected without using a different kind of members such as a staple and an eyelet, which would be an obstacle in recycle, so that it would be possible to provide a folding box for packing in which no staple and eyelet would be exposed outside, and thereby, a good appearance can be achieved.
Especially, it is possible to provide a folding box for packing in which further high durability superior in strength in connection and buckling can be achieved since the two box forming bodies (P1) and (P2) are connected in a plane by fusion into one body, and which can satisfy weather resistance, sanitary usage, light weight and durability of the high density foam polypropylene resin to secure not only recycle but also long-term returnability and reuse, as well as improve economy in physical distribution such as storage and transportation (collection) under a folded condition by reducing an effect of the elastic memory in bending the high density foam polypropylene resin to make the volume in folding small, and improve efficiency of folding and assembling (into a three-dimension) operations in handling.
Furthermore, a developed flat box forming board includes four side walls forming a square trunk of the folding box and comprises two box forming bodies (P1) and (P2) made of high density foam polypropylene resin and respectively comprising a main face wall (2) extendedly provided on one lateral side thereof with a connecting piece (1) for forming the trunk; a side face wall (3) connected with the other lateral side of the main face wall (2); bottom forming boards (4a) (4b) (4c) (4d) extendedly provided to respective lower edges of the above main face wall (2) and the above sub face wall (3); and cover forming boards (5a) (5b) (5c) (5d) extendedly provided to respective upper edges of the above main face wall (2) and the above sub face wall (3). Therefore, it is possible to easily produce the above respective box forming bodies (P1) and (P2), including respective portions provided thereto, without using any large dies.
[Effect of the Second Invention]
According to the second invention, the above two box forming bodies (P1) and (P2) in accordance with the first invention are formed as one box forming body (P3) comprising a first main face wall (21) extendedly provided on one side thereof with a connecting piece (1) for forming a trunk portion, a first sub face wall (31), a second main face wall (22) and a second sub face wall (32) in order. Therefore, it is possible to achieve the same operation and effect as the above first invention although a die for producing the box forming body would be large.
Effects of the structures of the folding box for packing according to the first invention and the folding box for packing according to the second invention are common in most parts. Thus, the operations and effects of the folding boxes for packing according to the both inventions can be described as follows by means of names of portions of the folding box for packing according to the first invention. That is, the line for bending into the shape of a V (8) includes a center groove (81) which is formed around a border line being to be a folding line and which has the width such that the folding member would not interfere each other, and auxiliary grooves (82), which are narrower than the width of the above center groove (81) and which are formed parallel on the folding surface side and on the both sides of the center groove (81) (refer to FIG. 3). Therefore, it is possible to reduce projection and interference due to bending of the member on the closely overlapping surface side of the above line for bending into the shape of a V (8), so that the effect of the elastic memory of the high density foam polypropylene resin can be erased to make the volume in folding lower.
Further, the line for bending into the shape of mountain (7a) (7b) includes two parallel side grooves (74) and a ridge (71a) (71b) therebetween formed along a border line being to be a line for bending into the shape of a mountain (refer to FIGS. 5 and 6), so that the side grooves (74) would intercept stretch memory operating on the bending part of the line for bending into the shape of mountain (7a) (7b), and thereby, the effect of the elastic memory of the high density foam polypropylene resin can be erased. In this arrangement, combined with the above arrangement, the thickness in folding can be maintained to be lower to keep the volume down.
As clearly shown in FIGS. 1, 2 and 9, the folding connecting piece (9a) (9b) extendedly provided to the inclined edge (6) having a 45 degrees angle in respect with the border line between the sub face wall (3) and the bottom forming board (4b) (4d) is extendedly provided so that a base end portion of the inclined edge (6), the base end portion being located closely to the above border line, would be left. Thus, the folding connecting piece (9a) (9b) is not sandwiched between the base end portions of the bottom forming board (4b) (4d) of the sub face wall (3) and the bottom forming board (4a) (4c) of the main face wall (2) in folding, so that the folding connecting piece (9) would not interfere with overlap of the bottom forming board (4b) (4d) of the sub face wall (3) and the bottom forming board (4a) (4c) of the main face wall (2). Therefore, the bottom forming boards (4a) (4b) (4c) (4d) at the above portion, the sub face walls (3), and the main face walls (2) are overlapped into a roughly piled layer, so that the volume due to the effect of the elastic memory at the above portion would be further reduced, and thereby, the volume increased at the above portion by inserting a member can be dissolved to assure flatting.
Further, a concave for fusion (10) in the shape of an outline of the folding connecting piece (9a) (9b) is formed on a front surface of the bottom forming board (4a) (4c) of the main face wall (2), the front surface overlapping a back surface of the folding connecting piece (9a) (9b) in assembling, and the back surface of the folding connecting piece (9a) (9b) is fused on the surface of the concave for fusion (10) (mainly refer to FIGS. 1 and 11), so that the folding connecting piece (9a) (9b) would enter into the above concave for fusion (10) to be fused. Thus, the thickness of the folding connecting piece (9a) (9b) sandwiched between the bottom forming board (4b) (4d) of the sub face wall (3) and the bottom forming board (4a) (4c) of the main face wall (2) is substantially thin while the bottom forming board (4b) (4d) of the sub face wall (3) and the bottom forming board (4a) (4c) of the main face wall (2) are overlapped into a rough piled layer. In this condition, the volume due to the effect of the elastic memory at the above portion would be reduced, and therefore, the cause of increase in volume can be further dissolved, so that the flatting degree in folding can be advanced.
Furthermore, lines for bending into the shape of a mountain (7a), the lines formed at the border lines between the respective main face walls (2), (21) and (22) and the respective sub face walls (3), (31) and (32) respectively adjacent to the main face walls (2), (21) and (22), including two parallel side grooves (74) and a ridge (71a) between the two side grooves (74) and forming corner portions (11) in folding, have the width of the ridge (71a) between the above two side grooves (74) around twice as wide as the wall thickness (refer to FIG. 5), so that a portion with large thickness of a piled layer, which is formed inside the above corner portion (11) in folding, that is, a portion with thickness of a piled layer, which is formed by a rough piled layer of the bottom forming board (4b) (4d) of the sub face wall (3), the bottom forming board (4a) (4c) of the main face wall (2) and the folding connecting piece (9a) (9b), would be covered by the ridge (71a) widened between the above two side grooves (74). Therefore, the effect of the elastic memory at the above portion can be reduced, which would greatly contribute to maintenance of flatting in folding.
Moreover, among the lines for bending into the shape of mountain (7c) between the respective face walls of the box forming bodies (P1) and (P2) and the cover forming boards (5a) (5b) (5c) (5d) and between the respective face walls and the bottom forming boards (4a) (4b) (4c) (4d), at least the former includes a middle groove (72), which is formed around a border line being to be a line for bending into the shape of a mountain (7c) and which has the width for erasing elastic memory of a member for folding, and side grooves (74), which are narrower than the width of the above middle groove (72) and which are formed parallel on the both sides of the middle groove (72), as clearly shown in FIG. 6. Thus, in the case of assembling into a three-dimension the folding box for packing having been folded into a flat shape, the cover forming boards (5a) (5b) (5c) (5d) operate so as to intercept the effect of the elastic memory by means of the middle grove (72) and the side grooves (74) on the both sides thereof. As a result, the cover forming boards (5a) (5b) (5c) (5d) lie down to open the box in the case of storing or taking out things while they lie down to close the box in the case of closing the covers. Thus, in operations of storing things and closing the covers in packing and operations of opening the covers and taking out things in taking out stored things, the cover forming boards (5a) (5b) (5c) (5d) do not disturb the above operations, so that smooth and efficient storing and taking out operations can be performed.
The folding box for packing has an auto bottom structure similarly in the both cases that the developed flat box forming board made of high density foam polypropylene resin comprises one box forming body (P3) and that it comprises two box forming bodies (P1) and (P2). For example, a punching blade or a thermal tooth form is used to punch the outline of the box forming body, and following to this or at the same time, a thermal tooth form is used to form lines for bending into the shape of V (8) and for folding into the shape of a mountain (7a) (7b) (7c) and concaves for fusion (10). Then, a front surface of the connecting piece (1) forms a space of a rough V-shaped side groove (74) together with a back surface of the sub face wall (3), and only opposing surfaces in this condition are heated by hot wind blowing or die heating (regardless of materials, but preferably formed from a metal plate in the view of a characteristic in manufacturing a die) before press and fusion for connection.
Next, the two box forming bodies (P1) and (P2) connected in a flat shape or one box forming body (P3) are or is assembled in a three-dimension so as to form a square cylindrical trunk, and set in an operational cradle so that the square cylinder portion of the trunk would cover the cradle. Then, the bottom forming boards (4a) (4c) of the main face walls (2) (21) (22) are bent toward the inner side in advance to be set in the operational cradle, and the bottom forming boards (4b) (4d) of the sub face walls (3) (31) (32) are bent toward the front surfaces of the above bottom forming boards (4a) (4c) of the main face walls (2) (21) (22) so as to overlap the bottom forming boards (4a) (4c) of the main face walls (2) (21) (22).
As clearly shown in FIG. 11, the folding connecting piece (9a) (9b) extendedly provided on the lateral side of the bottom forming board (4b) (4d) of the sub face wall (3) (31) (32) is raised up, using a line for bending into the shape of a V (8) as a standard line of rising, so that an angle between a back surface of the above folding connecting piece (9a) (9b) and a front surface of the bottom forming board (4a) (4c) of the main face wall (2) (21) (22) would be sharp, and so that the so formed space of a rough V-shaped groove (12) would be maintained. In this condition, only the back surface of the folding connecting piece (9a) (9b) and the front surface of the bottom forming board (4a) (4c) of the main face wall (2) (21) (22) are heated by the above-mentioned hot wind blowing or die heating to the extent that only surface portions respectively used for adhering are melted, and then, pressure-fused to complete a folding box for packing having an auto bottom structure.
The hot wind blowing or die heating and a pressure processing after heating for fusion between the front surface of the above connecting piece (1) and the back surface of the sub face wall (3) (32) opposing to the front surface of the connecting piece (1) and between the back surface of the folding connecting piece (9a) (9b) and the bottom forming board (4a) (4c) of the main face wall (2) (21) (22) are carried out either in an automatic process or in a manual process.